Arachidonic acid metabolism in isolated rat aorta. Dependence of prostacyclin biosynthesis on extracellular potassium concentration.
Slices of rat aorta were incubated in Krebs-Ringer bicarbonate buffer for measurements of immunoreactive 6-ketoprostaglandin F1 alpha, thromboxane (TX) B2, prostaglandin (PG)E2, and PGF2 alpha, and in Tris buffer (pH 9.3) for determination of prostacyclin (PGI2)-like activity. No significant generation of TXB2, PGE2, or PGF2 alpha by rat aortic tissue could be detected. The time-dependent release of 6-keto-PGF1 alpha Krebs-Ringer bicarbonate buffer closely correlated with PGI2 generation in alkaline Tris buffer. During a 30-min incubation period, 6-keto-PGF1 alpha, release was 79.8 +/- 3.3 pmol/mg at a buffer potassium concentration of 3.9 mmol/liter and significantly increased by 23% to 98.3 +/- 8.5 pmol/mg (P less than 0.025) in the absence of potassium in the incubation medium. A smaller decrease in buffer potassium concentration to 2.1 mmol/liter and an increase to 8.8 mmol/liter did not significantly alter aortic 6-keto-PGF1 alpha release. Changes in the incubation buffer sodium concentration from 144 mmol/liter to either 138 or 150 mmol/liter at a constant potassium concentration of 3.9 mmol/liter did not alter the recovery of 6-keto-PGF1 alpha. Our results support the concept that PGI2 is the predominant product of arachidonic acid metabolism in rat aorta. They further show that PGI2 can be recovered quantitatively as 6-keto-PGF1 alpha under the present in vitro conditions. In addition, this in vitro study points to the potassium ion as a modulator of vascular PGI2 synthesis with a stimulation at low potassium concentrations.
D000818:Animals; D001012:Aorta, Abdominal / Q000187:drug effects / Q000378:metabolism*; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D011464:Epoprostenol / Q000096:biosynthesis*; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D011188:Potassium / Q000494:pharmacology*; D011453:Prostaglandins / Q000096:biosynthesis*; D051381:Rats; D011919:Rats, Inbred Strains
D001095:Arachidonic Acids; D011453:Prostaglandins; D016718:Arachidonic Acid; D011464:Epoprostenol; D011188:Potassium